Color improvement of petroleum lubricating oils



U i ed COLOR IMPROVEMENT F PETROLEUM LUBRICATING ons Clinton H. Holder, Westfield, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Jan. 2, 1957, Ser. No. 631,994 Claims. (Cl. 208-286) This invention relates to an improved process for the finishing of petroleum lubricating oil base stocks especially with regard to upgrading and improving their color and stability. More particularly it relates to a process of this nature wherein the unfinished lube oil base stocks are first treated with aqueous alkali metal or alkaline earth hydroxides followed by hydrofining.

The treatment. of petroleum lube base stocks with aqueous caustic or lime is well known at this time for the improvement of the quality thereof. The hydrofining of teS atent 0 M 2,963,426 Patented Dec. 6,1960

tained in the oil. About twice, or less, of the theoretical amount of sodium hydroxide is used. Likewise potassium hydroxide is more reactive than sodium hydroxide. The concentration of the hydroxide in water is not critical and lies in the range of about 10% to 60%. 0 Generally, a 40 Baum strength caustic solution is used.

If lime is used it is dumped as a powder into a tank containing water and equipped with a paddle to form a water-line slurry representing 10 parts lime and 90 parts water. This slurry is then pumped into the oil line going to the furnace ahead of the pipe still. Thus the oil is first contacted with the lime slurry at about 300 F. and passes through the furnace where steam is added and it is heated to a coil outlet temperature of around 700 F. at a pressure of about one atmophere. The time of contact in the furnace above'600 F. conveniently isin the range of 30 to 120 sec.

The thus treated oil is then separated from the spent -metal hydroxide solution by distillation under reduced pressure in a vacuumppipe still. The lubricating oil fraction is taken off usually as a sidestream of one or more fractions. The alkali or alkaline metal oxide is nonvolatile and is in the small (generally 5% or less) such base stocks prior to hydrofining. By removing aromatic types the stock then becomes sufficiently responsive to hydrofining that the necessary quality improvement can be reached.

It has now been found that these petroleum lubricating oils can be upgraded, particularly with reference to color improvement, by treating them first with an aqueous metal hydroxide selected from the group consisting of hydroxides of alkali metals and alkaline earth metals, separating the oil from the treating medium by distillation whereby the oil isrerun in contact with the alkaline treating agent and hydrofining the rerun oil in the presence of a hydrofining catalyst. The results obtained are far superior to those resulting from the individual steps alone or from repeated utilization of each of the individual steps.

The petroleum lubricating oil base stocks treated are those known in the art. They may be distillates of any width falling within the boiling point range of about 625 to 1150 F. (equivalent atmospheric) or they may be higher boiling fractions recovered by deasphalting from residuum.

The material to be treated by this process can therefore represent any viscosity in the wide range of 35 up to 180 S.S.U. at 210 F. It applies most particularly to base stocks derived from the naphthenic base crudes such as Tia Juana, Coastal, Lagunillas, etc. It is not restricted to this class of crudes, however, since advantages are also derived by treating base stocks derived from paraffinic base crudes. Examples of particular lube base stocks which can be treated by this process are thus spindle oils, transformer oils, etc.

The oils are first treated with an aqueous hydroxide as mentioned previously. Because of cost considerations sodium hydroxide or lime (calcium oxide) are preferred. In general, lime is used in an amount of three to four times the theoretical to neutralize the acids confined in the conventional manner.

bottoms fraction. The oil is-thus rerun over the alkaline treating agent preparatory to the hydrofining treatment. The separated oil after this treatment is then hydro- For convenience the conditions are presented below.

Conditions in hydrofiner Broad Range Preferred Range Temperature, F. 500-750 600-725 Pressure, p.s.i.g 100-1. 500 400-800 Feed Rate, v./1r 0. 25-5 0.5-3 Hg Treat. s.c.f./b-. 100-3, 500 500-1. 500 Hg Consumption, s.c.f./b 10-1, 000 -150 'those of the nickel, tungsten sulfide type.

Regeneration of the fixed bed catalyst may be required periodically, depending largely upon the nature of the --feed stock. This regeneration is conveniently carried out at a temperature of about 750 to 1000 F. with an oxygen-containing gas.

In the hydrofining operation, the oil and hydrogen are contacted with catalyst by continuous flow through a vessel packed with catalyst. The oil feed to the reactor is preheated to the required temperature by means of a furnace or similar means. Hydrogen may or may not be heated prior to feeding to the reactor depending on the quantity used. The degree of contact of oil saturated with hydrogen with the catalyst is determined by the ratio of the oil flow rate to the catalyst volume.

After the hydrofining process has been carried out the liquid is then passed to a stripper to remove residual H S then it may be fractionated or kept intact.

The advantages of this invention will be better understood by reference to the following examples.

EXAMPLE A light Tia Juana raw lube distillate having a viscosity of 10 to 105 S.S.U. at F. (column I) was rerun over a lime-water slurry (8 parts lime and 92 parts water) representing four times the theoretical for neutralization of the organic acids. This was done in a batch laboratory distillation employing a vacuum of less than 1 mm. The bottoms yield was 4%. The rerun distillate "had'inspections shownin'column II. A portion of the latter was hydrofined over cobalt molybdate catalyst at 800 p.s.i.g., 800 s.c.f. hydrogen/b., a temperature of 650 F. and a feed rate of 1 v./v./hr. (column.III). A second portion was hydrofin'edlmderfthe' same-conditions except'the temperaturewas 575' F; "(column IV). Another portion ofthe' feed washydrofinedmnder the "same conditions as column 111 but was not given any lime treatment (column V). Inspection datalon these materials were as follows:

-' Hydrofining of Tia Juana lube distillate Q Hydro- Raw Rerun Hydrofined fined Dist. 'Dlst. Rerun Dist. Raw Inspections Dist.

I II III IV V Gravity, API 24. e 24. 2 27. 3 25. 9 27. 2 Visc., SSU:

- 102. 5 87.3 94.4 87.2 v 38. 2 37. 3 37. 7 37. 1 Vise. Index-. I 25. 8 48. 1 84.2 48 Neut. N0. mgs. KOH/g 1.6 0.18 .05 .06 .08 Color, T.R 6 9% 18% 18% 13 Colorhold, T.R. 4 8%; 17% 14 11% Pour Point, F 45 -45 35 -40 -40 Color stability test-actual color after 16 hours at 212 F.

These' data demonstrate that the: lime treatrnent alone gave a product of only 9 /2 Tag Robinson whereas hydrofining alone gave a Tag Robinson number of 13. Only the combination of thetwo steps :of this invention, columns III and IV, gave a Tag number of at least 18 or enough to satisfy specifications. Furthermore, the material produced at 650 F. and 1 v./v./hr. was shown to exhibit good color stability.

In other work it has been shown that spindle oils of this color can be made if the raw lube distillate is first extracted to a yield of about 80% before hydrofining. This is less desirable than the present process because the yields are reduced, extraction is more expensive than rerunning and solvent contamination in. the extraction plant becomes a problem when such light-stocks as this are extracted.

The advantages of this inventionWill-be apparent to the skilled in the art. It can be used in either of two ways. Either, improved products of superior'color characteristics are obtained in a simple, economical process, or, the use of the treatment with metal hydroxide before it This in turn yields products with less increase in pour point.

It is to be understood that this invention is not limited to the specific examples which have been offered merely as illustrations and that modifications may be made without departing from the spirit of the invention.

What is claimed is:

1. A process for upgrading andximproving the color of a petroleum lubricating oil basestock which comprises the steps of treating the oil with a substantial excess of an aqueous metal hydroxide beyond that required 'for neutralization, said metal hydroxide being selectedfrom the group consisting of hydroxides of alkali metals and alkaline earth metals at a temperature within the range of 300 to 700 F.; separating the thus treated oil from the aqueous metal hydroxide by distillation whereby the oil is rerun in direct contact with the alkaline treating agent and hydrofining the rerun oil in the presence of a hydrofining catalyst to produce an oil of improved color and in particular improved heat stability.

2. The process of claim 1 in which the metal hydrox- "ide treating step is conducted above 600 F. for to 'to 750"F. and a pressure in the range of 100 to 1500 hydrofining permits of mildcrconditions for the latter.

4."The process ofclaim' 3 is' in which the base stock has a viscosity of 35 to 180 S.S.U. at 210 F.

5. The method of bleaching a spindle oil which comprises treating the said oil with a substantial excess of a hydroxide-beyond that'required for neutralization, said hydroxide 'being selected from the class consisting of the aqueous hydroxides of alkali metals and alkaline earth'metals at temperatures above 600 F., and feed rates ofabout 1 v./v./hr. and the duration of the treatment isfrom 30 to 120 seconds, separating the thus treated oil from the aqueous metal hydroxides by distillation whereby the oil is rerun in direct contact with the alkaline treating agent and hydrofining the oil in the presence of a hydrofining catalyst at temperatures Within therange of 500-700 F. and a pressure within the range of to 1500 p.s.i.g.

' References Cited in the file of this patent UNITED STATES PATENTS 1,998,765 Logan -..Apr; 23, 1935 2,451,025 Ellender Oct. 12, 1948 2,654,696 La Porte Oct. 6, 1953 1,773,807 Blatz -*Dec. 11, 1956 

1. A PROCESS FOR UPGRADING AND IMPROVING THE COLOR OF A PETROLEUM LUBRICATING OIL BASE STOCK WHICH COMPRISES THE STEPS OF TREATING THE OIL WITH A SUBSTANTIAL EXCESS OF AN AQUEOUS METAL HYDROXIDE BEYOND THAT REQUIRED FOR NEUTRALIZATION, SAID METAL HYDROXIDE BEING SELECTED FROM THE GROUP CONSISTING OF HYDROXIDES OF ALKALI METALS AND ALKALINE EARTH METALS AT A TEMPERATURE WITHIN THE RANGE OF 300* TO 700*F., SEPARATING THE THUS TREATED OIL FROM THE AQUEOUS METAL HYDROXIDE BY DISTALLATION WHEREBY THE OIL IS RERUN IN DIRECT CONTACT WITH THE ALKALINE TREATING AGENT AND HYDROFINING THE RERUN OIL IN THE PRESENCE OF A HYDROFINING CATALYST TO PRODUCE AN OIL OF IMPROVED COLOR AND IN PARTICULAR IMPROVED HEAT STABILITY. 